Photosynthesis Comprehensive Notes Summary & Study Notes

🪴 Overview

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in carbohydrates. It sustains life on Earth by providing the oxygen we breathe and forming the base of the food chain.

⚡ Light-dependent Reactions

These reactions occur in the thylakoid membranes of the chloroplasts and require light. They capture light energy to produce ATP and NADPH, while splitting water to release O2 as a byproduct.

🧬 Calvin Cycle

Also known as the Calvin cycle or C3 pathway, it fixes carbon dioxide into sugars. It uses ATP and NADPH produced by the light reactions to synthesize G3P (glyceraldehyde-3-phosphate), a precursor to glucose and other carbohydrates.

🧪 Core Equation

$$6 CO_2 + 6 H_2O + light energy -> C_6H_12O_6 + 6 O_2$$

🧭 Chloroplast structure

The chloroplast houses the grana (stacks of thylakoids) and the stroma. The light reactions occur in the thylakoid membranes; the Calvin cycle runs in the stroma.

🌡️ Factors affecting rate

Photosynthesis rate depends on light intensity, CO2 concentration, and temperature. If any of these are limiting, the rate decreases.

🧠 Key concepts

Energy from photons is stored in the energy carriers ATP and NADPH; carbon fixation uses CO2 to build sugars.

❗ Common misconceptions

A common misconception is that plants only make sugar directly from light; in fact, light is converted to energy carriers that power carbon fixation, and oxygen is released.